Heating system

ABSTRACT

An improved compact heating system, particularly adapted for heating water and generating steam, includes a combustible gas supply zone, a combustion chamber therearound in the form of a hollow burner element having a plurality of radial channels in heat exchange relation with an array of heat exchange elements spaced peripheral therefrom, and gas ignition means. The channels are preferably of special configuration to improve heat transfer efficiency. The system is adapted to efficiently burn a high velocity stream of combustible gases and develop a wide range of B.T.U. outputs per hour, including multi-million B.T.U. output, while retaining advantages of larger types of heating systems. Improved baffles for heat exchanger elements are also provided.

O United States Patent [151 3,701,340 Miller 1 Oct. 31, 1972 [54]HEATING SYSTEM [72] Inventor: Avy Lewis Miller, 4090 Valley Examiner-leflneth P s Meadow Road, Encino, Calif. AttomeY'Dnald NM 91316 [57]ABSTRACT [22] Filed: June 8, 1970 A d h l l n improve compact eatingsystem, particu ar y [21] Appl' adapted for heating water and generatingsteam, in-

cludes a combustible gas supply zone, a combustion [52] US. Cl...122/367 C, 431/348 chamber therearound in the form of a hollow burner[51] Int. Cl ..F22b 21/00 element having a plurality of radial channelsin heat Field of Search 31/3 exchange relation with an array of heatexchange elements spaced peripheral therefrom, and gas ignitionRelflellus Cited means. The channels are preferably of specialconfiguration to improve heat transfer efficiency. The system UNITEDSTATES PATENTS is adapted to efficiently burn a high velocity stream of2,070,859 2/1937 Howe ..43l/348 combustible gases and develop a widerange of B T,U

Mekler X outputs per hour, including mukiqnillion out- 11.118 1 putwhile retaining advantages of larger types of heat- 3,160,145 12/1964 Mller ..122/367 ing systems Improved b ffl f0r heat exchanger 3,315,6464/1967 WItten, Jr ..122/235 ments are also provided 3,563,211 2/1971Hornbostel, Jr. ..l22/250 2/1971 Hoagland ..l22/250 10 Claims, 17Drawing Figures PATENIEDnm 31 m2 SHEET 10f 5 FlG.-l

INVENTOR.

AVY LEWIS MILLER A TTORNEY PATENTED um 3 1 m2 SHEET 3 0F 5 FlG.-3A

FlG.-'5

P'A'TENIEM m2 3.701. 340 SHEET BF 5 FIG.-l2

'INVENTOR. AVY LEWIS MILLER BY $116M A TTORNEY PATENTED BI I9123.701.340

sum 5 OF 5 INVENTOR.

AVY LEWIS MILLER A ni/5W ATTORNEY HEATING SYSTEM BACKGROUND llField ofInvention The present invention is directed to heating systems,particularly systems for heating water and generating steam, andcomponents thereof.

.2. Prior Art Conventional systems for heating water and generatingsteam are relatively bulky in relation to their B.T.U.

output. Certain advanced types of such systems impel combustible andcombusted gases therethrough at high velocity and, accordingly, canbemade much smaller and more compact. However, there has been a practi-SUMMARY OF THE INVENTION The Abstract herein summarizes certain featuresof the invention. The described heating system, although particularlyadapted as a water heating system, is also applicable to heating ofother liquids and generating of steam.

Such system is characterized, in part, by being ex-' tremely compact,and being capable of utilizing a high velocity stream of combustiblegases to provide a very high B.T.U. output over a wide range. Blowermeans are provided to force the gases through the hollow porous burnerelement, past the heat exchanger elements and out of the system. Suchburner element provides amultitude of combustion and combustion zonesand in one embodiment, baffles are provided in the pathways to increasetheir length and number, to promote turbulence and mixing and to radiateheat back into the multitude of combustion zones, thereby reducing thethe volume necessary to complete combustion. Preferably, the channelsare angled so that the combustion gases intersect the heat exchangerelements (surrounding the shield) at an angle or tangentially toincrease the heat exchange flow path and efficiency. The elements may befinned and with or without baffle elements. It is a part of theinvention to provide baffles for heat exchanger elements, which bafflesare of improved configuration, to provide increased gas turbulence.Return conduits may be disposed peripheral of the elements andinterconnected therewith through headers to provide thermal circulationfor theheat transfer medium (water), particularly suitable whereexternal pump means are not provided. Moreover, the system provides easyaccess for cleaning of the heat exchanger elements, ready replacementthereof and easy access for sludge removal.

DRAWINGS construction thereof;

FIG. 2 is an enlarged fragmentary sectional view of the heating systemof FIG. 1;

FIG. 3 is a fragmentary section taken along the section line 3-3 of FIG.2;

FIG. 3a is a fragmentary section of a further embodiment of the stack ofburner element discs;

FIG. 4 is an enlarged section taken along the section line 4-4 of FIG.3;

FIG. 5 is an enlarged section taken along the section line 5-5 of FIG.3a;

FIG. 6 is an enlarged section taken along the section line 66 of FIG.3a;

FIG. 7 is an enlarged section taken along the section line 7 -7 of FIG.3a;

FIG. 8 is an enlarged fragmentary perspective of a portion of the burnerelement of FIG. 1;

FIG. 9 is an enlarged fragmentary perspective of a modified form of aportion of the burner element of the present system;

FIG. 10 is a plan view of a portion of the burner element of FIG. 9;

FIG. 11 is a section taken along the section line I l-- 11 of FIG. 10;

FIG. 12 is a schematic fragmentary perspective of a further embodimentof the burner element of the system of the invention;

FIG. 13 is a schematic fragmentary section of a double row of finned andunfinned heat exchanger elements in the system of the invention;

FIG. 14 is a schematic fragmentary section of heat exchanger elementsemploying baffles of improved configuration;

FIG. 15 is a schematic section illustrating the use of return conduitsin association with heat exchanger elements in the present system; and

FIG. 16 is an enlarged fragmentary schematic perspective of a modifiedarrangement of heat exchanger elements and header rings with baffles forclosed loop multi-pass circulation of water or other fluid in thepresent system.

DETAILED DESCRI TION The System in General Now referring to thedrawings, FIG. 1 schematically illustrates in side elevation, partlybroken away, a

preferred embodiment of the heating system of the invention. As shown inFIG. 1, a heater 20 is provided, which includes a central gas supplyzone 22 to which is connected a gas supply duct 24 leading from a blower26. Zone 22 is defined by a burner element 28,

preferably cylindrical in configuration. An array of through header 34and hot water removal means (not shown) through header 36. Refractory(such as silica, etc.) layers 37 and 39 are disposed at the lower andupper ends, respectively, of burner element 28 within headers 34 and 36,respectively, layer 39 having an aperture through which duct 24 extends.Layers 37 and 39 are backed by heat insulative layers 41 and 43,respectively, fabricated of, for example, mineral wool or the like.

A space 38 is provided between elements 30 and an insulated jacket 40comprising two spaced walls 42 and 44 connected at their lower ends to abase plate 46 resting on support legs 48 and connected at their upperend to a similarly constructed jacket 50 comprising walls 52 and 54. Anair inlet 56 communicates with a passageway 58 between walls 42 and 44and an interconnected passageway 60 between walls 52 and 54, thosepassageways in turn being connected to an inlet duct 62 leading toblower 26 disposed outside jackets 40 and 50. Combustion ignition means(not shown) are also provided. A gas outlet duct 64 is also provided, asshown in FIG. 1.

Jackets 40 and 50, base plate 46, legs 48, ducts 24, 62, 64 and blower26 can be fabricated of any suitable conventional materials such assteel, iron, etc., in a conventional manner. Blower 26 can be powered inany suitable manner. It delivers combustible gases (air or oxygen andnatural gas, etc.) at a high velocity, for example, 0.277 cubicfeet/second for a unit having a total contained volume of 4.4 cubic feetand capable of putting out 800,000 B.T.U./hour.

Burner Element Element 28 is more particularly illustrated in enlargedfragmentary view in FIG. 2. Such element can, for example, comprise aplurality of stacked refractory blocks which form discs 66 defining aplurality of combustion channels 68 communicating between zone 22 andthe space 70 between shield 28 and elements 30, as shown in FIGS. 1 and2. Alternatively, element 28 can be fabricated of a single piece ofrefractory material, suitably apertured in accordance with thesucceeding description. Discs 66 can be fabricated of any suitablerefractory material such as hardened brick, silica blocks, etc.

Channels 68 are provided with enlarged combustion zones 72 whereincombustion is initiated, as by conventional electrical ignition means(not shown) or the like. Discs 66 are held together in vertical stackedrelation, as by bolts 74 passing therethrough (FIG. 3a, bolts 74a), andsecured thereto by nuts 76 (in FIG. 3a nuts 76a). FIGS. 3 and 3acombined show a typical spacing for such securing means. Althoughchannels 68 can be provided in any suitable manner, as by drilling outthe centers of each block or disc in the stack, it is preferred to castor otherwise form discs 66 such that the upper and lower surfaces ofeach disc cooperate with the adjoining surfaces of adjacent discs 66 inthe stack to provide channels 68 and zones 72.

Preferably, burner element 28 is hollow and cylindri- .cal, as shown inFIGS. 3 and 3a with channels 68 (68a in FIG. 3a) distributed uniformlytherearound. Also, preferably, each such channel is configured toprovide (in FIG. 3) a narrow inner passageway 78 between zone 22 andzone 72 (in FIG. 3a passageway 78a, zone 22a and zone 72a). The outerperiphery of each zone 72 (or 72a) is defined by a buffer plate 80 (or80a, as in FIG. 3a) positioned such that combustion gases flowingoutwardly are deflected into a plurality of streams passing from element28 tangentially through angled passageways 82 between plates 80 (asshown in FIG. 3) for contact with heat exchanger elements 30 at an acuteangle or tangentially in order to increase the flow path of such gases,increase turbulent mixing, eliminate laminar flow, and increase heatexchange efficiency with elements 30.

FIG. 4 shows narrow passageways 78; FIG. 5 shows angled passageways 82aand buffer plates 800; FIG. 6 shows passageways 78a of larger diameterthan passageway 78 (of FIG. 3); and FIG. 7 shows passageways 78a, zone72a and buffer plate 800. A schematic fragmentary perspective view isshown in FIG. 8 of passageways 78 and 82 and buffer plates along withcombustion zones 72. It will be noted that disc 66 is, as shown in FIG.8 and in FIG. 3, recessed around that portion 83 containing passageway78 such that portion 83 in each instance assumes the shape of aninwardly directed nozzle. It is necessary to have passageway 78relatively long and of sufiiciently small diameter to assure that anycombustion gases attempting to pass back therethrough are cooled bycontact with the relatively large surface area of portion 83 definingpassageway 78 to a point below that which would cause ignition of gasesin zone 20 and an explosion therein.

A modified form of a portion of a pair of discs comprising part of theburner element is shown in schematic perspective view in FIG. 9. Eachsuch disc 66b forms with the next adjoining disc 66b in the stack, achannel 68b comprising a narrow inner passageway 78b (to preventcombustion from migrating back into gas supply zone 22 and initiating anexplosion), an enlarged combustion zone 72b generally of sphericalconfiguration and an exit passageway 82b angled from the direction offlow of passageway 78b, as shown more particularly in FIGS. 10 and 11.Passageway 78b preferably connects with zone 72b along only a smallportion thereof and the walls defining passageway 78b preferably divergeoutwardly. Accordingly, a swirling motion of hot gases is set up in zone72b to increase combustion, while the shape of passageway 82b is such asto increase gas velocity.

The described improvements all contribute to increased burning of thegases in chamber 32 so as to minimize the necessary volume thereof for agiven B.T.U. output and they also contribute to increased efficiency ofheat transfer through elements 30 by improving gas turbulence, mixing,suppression of laminar flow, increasing the contact of hot gases withthe heat exchanger elements, etc.

The burner element of the system of the invention may also be ofsomewhat different form, such as that shown in FIG. 12, wherein aperforated, hollow cylindrical high temperature metal element 84 (forexample, steel) is schematically illustrated. Element 84 channels gasesfrom gas supply zone 86 therein through spaced holes 88 so as toprovide, taken with array of heat exchanger elements 90 spaced outwardlytherefrom, a plurality of combustion foci. Such element 84 is ofsubstantially simpler design than that of element 28 and does not offersome of the advantages of element 28 (e.g. tortuous gas flow path,radiation deflection, gas deflection with angled gas contact withelements 90, etc.).

It will be understood that element 84 can, if desired, be in the form ofany high temperature metal, ceramic or the like hollow porous (orperforated) self-supporting structure, for example, a steel grid or meshscreen hollow cylinder or the like. It will be also understood thatalthough a hollow cylindrical configuration for this element is mostdesired, with the array of heat exchanger elements spaced outwardlytherefrom and entirely surrounding the same, hollow square, polygonal orother configurations for the burner element will perform satisfactorily.Moreover, the array of heat exchanger elements need not entirely enclosethe burner element, although such array is the most efficient and themost compact.

HeatExchangerElements Regarding the heat exchanger elements, suchelements 30 are shown in FIGS. 1 and 2 as hollow tubular memberscontaining fins 94 to increase the efficiency of heat exchange withcombustion gases in space 70.

As schematically illustrated in fragmentary section in FIG. 13, sucharray may be modified to include an inner circular array of spacedunfinned hollow tubular members 96, backed by an outer circular array ofmore closely spaced finned hollow tubular members 98 spaced outwardlyfrom members 96. With such an arrangement, initial heat exchange isaccomplished between the combustion gases and the unfinned member 96when the gases are hottest. In the area of unfinned'members 96 thetemperature of the combustion gases is very high (e.g. 2,600F.). Wateror other heat exchange medium is passed (e.g. forced) through tubes 96at a high enough flow rate to prevent conversion-into steam or othergases. For this purpose, a water impeller pump or the like ofconventional design can be used (not shown).

By the time the combustion gases pass out of heat exchange relationshipwith tubes 96, such gases have decreased in temperature a considerableextent (to e.g. l,200.F. or the like). Such cooler gases then contactfinned tubes 98 where, because of the greater surface area of such tubesdue to the fins, improved heat exchange efficiency is accomplished so asto extract most of the remaining heat from the combustion gases andtransfer the same to the heat transfer medium e. g. water flowingrapidly through tubes 98, as by an impeller pump or the like (notshown). The cooled gases which may be at about 400500F., for example, or

less, but in any event above the dew point to eliminate corrosionproblems in the exhaust gas ducts then pass into space 38 and exit thesystem through outlet duct 64. With such a double array, finned andunfinned steel tubes can be used efficiently, thus providing a saving incost. Steel finning on tubes, due to its lower heat transfer efficiency,as opposed to copper, tends to heat of time, if such finning is used ontubes without an inner buffer array of unfinned tubes to first drop thetemperature to below a level which causes excess heating of the finning.

Heat exchange efficiency with elements 30 ortubes 96 and98 isparticularly high if such gases strike the heat exchanger elements at anangle, such as is effected by angling passageways 82 as previouslydescribed. A longer heat transfer pathway results, laminar flow isprevented and turbulent mixing of combustion gases occurs, all of whichimprove efficiency of heat transfer. Such heat transfer is furtherenhanced by the use of the double row of members 96 and 98 andappropriate positioning of individual members 96 and 98, such that thepath of the combustiongases is further segmented and eachpathlengthened.

Increases in heat exchange efficiency can also be provided by providingelements 30 or elements 98 with I up high enough to cause it to flakeaway over a period baffles 100, such as are schematically illustrated insection in FIG. 14. It will be understood that unfinned elements 96 canalso be provided with similar baffles instead of or in addition to thoseprovided elements 30 or 98. Baffles can be of any suitable configurationto bridge partially or wholly the spaces 99 between adjacent elements30,as shown in FIG. 14, and spaced therefrom on the side of the array awayfrom burner element 28. The baffles are configured to lengthen and,preferably, divide the combustion gas flow path for increased length ofintimate contact with elements 30, particularly fins 94, and to alsoinduce turbulent mixing to decrease further the possibility of laminarflow. In this regard, it will be noted that with baffles 100 in place,the side of the finned elements 30 away from burner element 28 is nowexposed fully to the combustion gases, since they are deflected thereto,for increased heat transfer. Moreover, baffles 100 are preferably of thespecial configuration shown in FIG. 14. Thus, baffles 100 may eachcomprise an elongated configured plate of durable high temperaturemetal, such as copper or the like, and comprising a central spine 101and a pair of laterally and rearwardly extending curved wings 103 and105 interconnected atspine 101. Tips 107 and 109 of wings 103 and 105,respectively, are reflected forwardly, so that each wing is configuredas a semi-closed loop. Gases passing through spaces 99 strike spine 101and are divided into two paths, one along each wing. As the combustiongases follow each such path, the wing and tip not only cause them tointersect the adjoining surfaces of the heat exchanger elements 30 andtheir fins, but force the gases back into the spaces 99 to causeturbulent mixing with further combustion gases in those spaces, thusincreasing heat transfer. Gaps 111 between adjacent baffies 100 permitthe combustion gases to exit the area. Baffles 100 account forsubstantial increases in heat transfer efficiency, maximizing theintimate contact between elements 30 and such gases over the entiresurface of elements 30. Such heat exchanger baffles can improve heattransfer efficiency as much as 30 percent or more.

Elements 30, 96 and 98 can be fabricated of any' suitable durable hightemperature heat transfer material, such as copper, as can fins 94 andbaffles .100. Obviously, the material selected must be capable ofwithstanding the impingement of hot combustion gases over along periodof time while providing for efficient heat transfer. Resistance tocorrosion by the combustion gases and also the heat transfer medium,such as water, passing therethrough is essential. Return Conduits Aspreviously described, elements 30 are interconnected through headers 34and 36 adjacent the bottom and top, respectively, of heater 20. Withsuch an arrangement, system 20 is enclosed in a water jacket, except forthe insulative layers 37, 39, 41 and 43 within the annular headers. Apreferred arrangement of components is also schematically illustrated insection in FIG. 15 wherein return conduits 102 are shown spacedoutwardly from the array of finned elements 30 but in the flow path ofcombustion gases after the latter pass by elements 30. Conduits 102conduct aheat transfer medium, such as water, between headers 34 and36and can be fabricated of any suitable high temperature I then throughheader 36 then down through conduits 102, then through header 34 andfinally up again through elements 30. This thermal circulation systemeffectively channels any pockets of steam formed in the liquid medium,(steam from water) to the cooler headers where the steam is eliminated.

A further particular embodiment of the described closed loop thermalcirculation system is schematically illustrated in FIG. 16 in isolatedperspective view. With the arrangement shown in FIG. 16, rapid flow ofthe heat transfer medium in the heat exchange tubes prevents build-upscale on the tubes and simplified maintenances of the system. As shownin FIG. 16, an annular hollow tubular bottom header 104 is connected toa water inlet tube 106 and is provided with three internal baffles 108,110 and 112 which divide header 104 into two equal semi-circularcompartments and further divide one of these compartments into two equalsubcompartments. A plurality of hollow heat exchanger tubes 114 arespaced along the upper surface of header 104, are in connection with theinterior thereof and extend upwardly therefrom into contact with thelower surface and also the interior of a top header 1 16 of likeconfiguration to header 104. Header 116 is divided into two equalsemi-circular compartments by means of baffles 118 and 120. Baffle 118is aligned with baffle 108. A water outlet tube 112 is secured to header104, also as shown in FIG. 16, within subcompartment 124 while waterinlet 106 is disposed within subcompartment 126.

With such an arrangement occupying a location in heater system 20comparable to that of elements 30 and headers 34 and 36, an essentiallyclosed loop multipass flow system for the heat transfer medium isprovided. Thus, water (or other heat transfer medium) entering throughinlet tube 106 rises in the tubes in subcompartment 126 passes throughcompartment 128 of header 116 and down the downflow tubes therein,passes through compartment 130 of header 104, up through the upflowtubes therein, then through compartment 132 of header 116 and downthrough the I downflow tubes therein to subcompartment 124 where HeatSystem It will be noted that positioning of the multicombustionzone-fomiing burner element within and spaced from the array of heatexchanger elements 30 to form therewith the combustion chamber 32 ofcontrolled configuration (including elongated channels with multiplecombustion zones, baffles, angled flow paths, etc.) without having toprovide a separate such combustion chamber maximizes heat transfer andcombustion efficiency per unit volume. High flow through velocities forcombustion gas and water or other heat transfer medium are possible, sothat multi-million B.T.U./hour outputs can be provided with the presentsmall, light compact units while still providing easy access and repairfor the heat exchange tubes (since they surround the burner element andhave their bottom and top ends connected to the headers through whichaccess is gained) and permitting sludge removal from the system throughthe heat exchanger tubes and headers and replacement of such tubes asnecessary. For example, a water heating unit of the present designhaving the following dimensions and operated within the followingparameters, can produce B.T.U./hour very efficiently:

IMPROVED HEATER Burner Element Height 21 inches 0. D. 7 inches 1. D. 5inches Construction material ceramic refractory Heat Exchanger TubeArray Spacing from burner element 1 1/16 inch Number and spacing oftubes l8 tubes spaced with 1/16 inch gaps O. D. of tube and length 1inch 21 inches I. D. of tube 78 inch Radius of fin 5/16 inch, 7 fins perinch Construction material copper Heater Dimensions (O.D.) 20 inches X24 inches Combustion Gas Flow Rate 1000 cu.ft. of natural gas/hour.

Water Flow Rate gals/min.

B.T.U. Output 800,000 B.T.U./hour The present improved heater isinexpensive to build, operate and maintain, can be run continuously overlong periods of time on bottled gas, natural gas, propane or othercombustible gas mixture without clean-up or maintenance and because ofthe high flow rate of water or other heat transfer medium therethrough,resists build-up of scale or corrosion of components. Moreover, thecomponents thereof are few and are durable, and access thereto forinspection, maintenance and replacements and removal of sludge issimple. The heater is ideal for such uses as pool heating and the likewhere space is at a premium. Because of its small size, it can beshipped assembled or in fewer subassembled components at less cost andcan be installed and run at a lower than conventional price. Itscomponents can be constructed of readily available materials in aninexpensive manner. Such heater fills a long-felt need for improvedheating efficiency and compactness in the water heating and alliedfields. Thus with the present system, B.T. U. outputs comparable tothose of the most compact and efficient commercial units can be obtainedutilizing a volume one fourth to one fifth as large as such units.Moreover, the present system requires less excess air than certaincommercial units and provides increased efiiciency. Accordingly, thepresent system has many advantages over commercial units.

What is claimed is:

1. An improved compact heating system comprising in combination;

a. A generally centrally disposed combustible gas supply zone;

b. A peripheral combustion chamber comprising:

i. A hollow porous walled burner element com prising a plurality ofstacked refractory hollow discs adjacent said gas supply zone anddefining a plurality of spaced generally radially disposed channelsbetween at least some of adjacent discs wherein combustion isinitiatable;

2. Combustion ignition means in communication with said channels;

3. A plurality of heat exchanger elements disposed around said burnerelement in an array spaced outwardly from said channels but in heatexchange relationship therewith;

c. Means for conducting a heat transfer medium into and through saidheat exchange elements and out of said system;

d. Blower means for introducing combustible gases to said gas supplyzone and exhausting combusted gases at a high flow rate from saidsystem; and,

e. An outer heat insulative shield disposed around and spaced outwardlyfrom said combustion chamber to define a gas collection space, saidspacing being" sufficient such that said shield is relatively thin andsaid system is relatively light and compact.

2. An improved compact heating system comprising in combination;

a. A generally centrally disposed combustible gas supply zone;

b. A peripheral combustion chamber comprising:

1. A hollow porous walled burner element comprising stacked refractorydiscs adjacent said gas supply zone and defining a plurality of spacedgenerally radially disposed channels between at least some of adjacentdiscs wherein combustion is initiatable;

2. Combustion ignition means in communication with said channels;

3. A plurality of heat exchanger elements disposed around said burnerelement in an array spaced outwardly from said channels but in heatexchange relationship therewith;

c. Means for conducting a heat transfer medium into and through saidheat exchange elements and out of said system;

d. Blower means for introducing combustible gases to said gas supplyzone and exhausting combusted gases from said system at a high flowrate; and

e. An outer heat insulative shield disposed around and spaced outwardlyfrom said combustion chamber, at least a portion of said channels beingangled such that the combustion, gases passing therefrom intersect saidheat exchanger elements tangentially, thereby facilitating turbulentmixing and heat transfer.

3. The improved heating system of claim 2 wherein baffles are disposedwithin said channels in said burner element whereby gas combustion isfacilitated.

4. The improved heating system of claim 2 wherein said channels includeelongated narrow inner passageways, enlarged zones wherein combustion isinitiated connected to said inner passageways and to said angled exitchannels.

5. The improved heating system of claim 4 wherein each of said enlargedzones is generally spherical and wherein the portion of said channelbetween said zone and the outer periphery of said burner element communicates with said zone over a limited area and is defined by outwardlydiverging walls.

6. The improved heating system of claim 1 wherein said heat exchangerelements are disposed around said burner element in a first seriescomprising spaced generally tubular non-finned elements adjacent saidshield and a second series comprising spaced generally tubular finnedelements separated from said shield by said first series.

7. The improved heating system of claim 6 wherein said finned andunfinned elements are fabricated of steel.

8. An improved compact heating system comprising in combination;

a. A generally centrally disposed combustible gas supply zone;

b. A peripheral combustion chamber comprising:

1. A hollow porous walled generally cylindrical burner elementcomprising stacked refractory discs, disposed around said gas supplyzone and defining a plurality of spaced generally radially disposedchannels wherein combustion is in itiatable;

2. Combustion ignition means in communication with said channels;

3. A plurality of heat exchanger elements disposed around substantiallythe entire periphery of said burner element in a generally cylindricalarray spaced outwardly from said channels but in heat exchangerelationship therewith;

c. Means for conducting hot water into and through said heat exchangeelements and out of said system;

d. Blower means for introducing combustible gases to said gas supplyzone and exhausting combusted gases at a high flow rate from saidsystem;

c. An outer heat insulative shield disposed around said combustionchamber; and,

f. Baffles disposed in said channelsto elongate and divide gas flowpaths in said burner element, at least a portion of said channels beingangled to cause said combustion gases to intersect said heat exchangerelements at an angle.

9. The improved heating system of claim 8 wherein said heat exchangerelements are interconnected through spaced headers at opposite endsthereof, and wherein a plurality of water return conduits are disposedperipheral of said heat exchanger elements and interconnected therewiththrough said headers, whereby steam entrainment in said heat exchangerelements is avoided.

10. The improved heating system of claim 8 wherein said heat exchangerelements are spaced about uniformly along the surface of andinterconnected through first and second spaced annular headers atopposite ends thereof, wherein each said header includes a plurality ofbaffles dividing said header into separate compartments, wherein saidheader baffles of said first header are positioned with respect to saidbaffles of

1. A hollow porous walled burner element comprising a plurality ofstackeD refractory hollow discs adjacent said gas supply zone anddefining a plurality of spaced generally radially disposed channelsbetween at least some of adjacent discs wherein combustion isinitiatable;
 1. An improved compact heating system comprising incombination; a. A generally centrally disposed combustible gas supplyzone; b. A peripheral combustion chamber comprising:
 2. Combustionignition means in communication with said channels;
 2. Combustionignition means in communication with said channels;
 2. An improvedcompact heating system comprising in combination; a. A generallycentrally disposed combustible gas supply zone; b. A peripheralcombustion chamber comprising:
 2. Combustion ignition means incommunication with said channels;
 2. Combustion ignition means incommunication with said channels;
 3. A plurality of heat exchangerelements disposed around said burner element in an array spacedoutwardly from said channels but in heat exchange relationshiptherewith; c. Means for conducting a heat transfer medium into andthrough said heat exchange elements and out of said system; d. Blowermeans for introducing combustible gases to said gas supply zone andexhausting combusted gases at a high flow rate from said system; and, e.An outer heat insulative shield disposed around and spaced outwardlyfrom said combustion chamber to define a gas collection space, saidspacing being sufficient such that said shield is relatively thin andsaid system is relatively light and compact.
 3. A plurality of heatexchanger elements disposed around said burner element in an arrayspaced outwardly from said channels but in heat exchange relationshiptherewith; c. Means for conducting a heat transfer medium into andthrough said heat exchange elements and out of said system; d. Blowermeans for introducing combustible gases to said gas supply zone andexhausting combusted gases at a high flow rate from said system; and, e.An outer heat insulative shield disposed around and spaced outwardlyfrom said combustion chamber to define a gas collection space, saidspacing being sufficient such that said shield is relatively thin andsaid system is relatively light and compact.
 3. The improved heatingsystem of claim 2 wherein baffles are disposed within said channels insaid burner element whereby gas combustion is facilitated.
 3. Aplurality of heat exchanger elements disposed around said burner elementin an array spaced outwardly from said channels but in heat exchangerelationship therewith; c. Means for conducting a heat transfer mediuminto and through said heat exchange elements and out of said system; d.Blower means for introducing combustible gases to said gas supply zoneand exhausting combusted gases from said system at a high flow rate; ande. An outer heat insulative shield disposed around and spaced outwardlyfrom said combustion chamber, at least a portion of said channels beingangled such that the combustion gases passing therefrom intersect saidheat exchanger elements tangentially, thereby facilitating turbulentmixing and heat transfer.
 3. A plurality of heat exchanger elementsdisposed around substantially the entire periphery of said burnerelement in a generally cylindrical array spaced outwardly from saidchannels but in heat exchange relationship therewith; c. Means forconducting hot water into and through said heat exchange elements andout of said system; d. Blower means for introducing combustible gases tosaid gas supply zone and exhausting combusted gases at a high flow ratefrom said system; e. An outer heat insulative shield disposed aroundsaid combustion chamber; and, f. Baffles disposed in said channels toelongate and divide gas flow paths in said burner element, at least aportion of said channels being angled to cause said combustion gases tointersect said heat exchanger elements at an angle.
 4. The improvedheating system of claim 2 wherein said channels include elongated narrowinner passageways, enlarged zones wherein combustion is initiatedconnected to said inner passageways and to said angled exit channels. 5.The improved heating system of claim 4 wherein each of said enlargedzones is generally spherical and wherein the portion of said channelbetween said zone and the outer periphery of said burner elementcommunicates with said zone over a limited area and is defined byoutwardly diverging walls.
 6. The improved heating system of claim 1wherein said heat exchanger elements are disposed around said burnerelement in a first series comprising spaced generally tubular non-finnedelements adjacent said shield and a second series comprising spacedgenerally tubular finned elements separated from said shield by saidfirst series.
 7. The improved heating system of claim 6 wherein saidfinned and unfinned elements are fabricated of steel.
 8. An improvedcompact heating system comprising in combination; a. A generallycentrally disposed combustible gas supply zone; b. A peripheralcombustion chamber comprising:
 9. The improved heating system of claim 8wherein said heat exchanger elements are interconnected through spacedheaders at opposite ends thereof, and wherein a plurality of waterreturn conduits are disposed peripheral of said heat exchanger elementsand interconnected therewith through said headers, whereby steamentrainment in said heat exchanger elements is avoided.
 10. The improvedheating system of claim 8 wherein said heat exchanger elements arespaced about uniformly along the surface of and interconnected throughfirst and second spaced annular headers at opposite ends thereof,wherein each said header includes a plurality of baffles dividing saidheader into separate compartments, wherein said header baffles of saidfirst header are positioned with respect to said baffles of said secondheader and wherein said first header is connected to a water inlet and awater outlet in separate compartments of said headers whereby amulti-pass high velocity flow path between said headers through saidheat exchanger elements is provided.